Kidneys of the human body function to remove excess fluids as well as some ions. The functional unit of the kidney is the nephron. A nephron consists of a filtering unit of tiny blood vessels called a glomerulus attached to a tubule. When blood enters the glomerulus, it is filtered and the remaining fluid then passes along the tubule. In the tubule, chemicals and water are either added to or removed from this filtered fluid according to the body's needs, and the final product is urine, which is excreted.
In patients with chronic kidney disease, kidney function is severely compromised. Chronic kidney disease, also known as chronic renal disease, is a progressive loss in renal function over a period of months or years. The most severe stage of chronic kidney disease is End Stage Renal Disease, which occurs when the kidneys cease to function.
The two main causes of chronic kidney disease are diabetes and high blood pressure, which are responsible for up to two-thirds of the cases. Heart disease is the leading cause of death for all people having chronic kidney disease. Excessive fluid can accumulate in patients suffering from end stage renal disease. The mortality rate of end stage renal disease patients who receive traditional hemodialysis therapy is 24% per year with an even higher mortality rate among diabetic patients.
Fluid accumulates in end stage renal disease patients because the kidneys can no longer effectively remove water and other fluids from the body. The fluid accumulates first in the blood and then accumulates throughout the body, resulting in swelling of the extremities and other tissues as edema. This accumulation of fluid causes increased stress on the heart, in turn causing significant increases in blood pressure or hypertension, which can lead to heart failure.
Although the population of patients afflicted with chronic kidney disease grows each year, there is no cure. Current treatments for chronic kidney disease seek to slow the progression of the disease. However, as the disease progresses, renal function decreases, and, eventually, renal replacement therapy is employed to compensate for lost kidney function. Renal replacement therapy entails either transplantation of a new kidney or dialysis.
Methods to treat kidney disease require the processing of blood to extract waste components such as urea and ions. The traditional treatment for kidney disease involves dialysis
Dialysis emulates kidney function by removing waste components and excess fluid from a patient's blood. This is accomplished by allowing the body fluids, usually the blood, to come into the close proximity with the dialysate, which is a fluid that serves to cleanse the blood and actively remove the waste components and excess water. During this process, the blood and dialysate are separated by a dialysis membrane, which is permeable to water, small molecules (such as urea), and ions but not permeable to the cells. Each dialysis session lasts a few hours and may be repeated as often as three times a week.
Traditional processes, such as dialysis, require extracorporeal processing of body fluids. Once the blood is purified, it is then returned to the patient. Although effective at removing waste components from blood, dialysis treatments are administered intermittently and, therefore, do not emulate the continuous function of a natural kidney. Once the dialysis session is completed, the fluid begins to accumulate again in the tissues of the patient.
The benefits of dialysis notwithstanding, statistics indicate that three out of five dialysis patients die within five years of commencing treatment. Studies have shown that increasing the frequency and duration of dialysis sessions can improve the survivability of dialysis patients. Increasing the frequency and duration of dialysis sessions more closely resembles the continuous kidney function sought to be emulated. However, the extracorporeal processing of the body fluids increases the discomfort, inconvenience and the costs associated with treatment. There is also an additional risk of infection, which mandates that the procedures be carried out under the supervision of trained medical personnel.
Wearable dialysis units have been conceived in which the various components of the dialysis unit are miniaturized and made portable. The utility of these units remains limited due to the requirement that the blood must be brought outside of the body for filtering and due to the necessity for frequent servicing of the parts.
An alternative to a wearable dialysis system is an implantable dialysis device. With conventional implantable dialysis devices, most of the components are implanted, and the blood does not leave the patient's body. This type of unit suffers from difficulties related to the need for surgery to replace the internal parts, generally resulting from growth of tissue over the surfaces of the device that are exposed to tissue fluids, which results in reduced efficiency of the filtration.
Another clinical solution for kidney disease is peritoneal dialysis. In peritoneal dialysis, dialysate is infused into the peritoneal cavity. The peritoneal membrane serves as a natural dialyzer, and waste components diffuse from the patient's bloodstream across the peritoneal membrane into the dialysis solution via an osmotic gradient.
Under local anesthesia, a many-eyed catheter is sutured in place in the peritoneum and a sterile dressing is applied. The amount and the kind of dialysate and the length of time for each exchange cycle vary with the age, size, and condition of the patient.
There are three phases in each cycle. During inflow, the dialysate is introduced into the peritoneal cavity. During equilibration (swell), the dialysate remains in the peritoneal cavity. By means of osmosis, diffusion, and filtration, the needed electrolytes pass via the vascular peritoneum to the blood vessels of the abdominal cavity, and the waste products pass from the blood vessels through the vascular peritoneum into the dialysate.
During the third phase (drain), the dialysate is allowed to drain from the peritoneal cavity by gravity. The dialysis solution is removed, discarded, and replaced with fresh dialysis solution on a semi-continuous or continuous basis. Patients are able to replace the fluid periodically and care for the access ports.
This particular treatment causes discomfort due to excess amounts of fluid being pumped in and out of the abdominal area and retrograde flow into the bloodstream, which can increase fluid retention and the risk of infections. Further, medication for pain may be necessary.
Peritoneal dialysis may result in several complications, including perforation of the bowel, peritonitis, atelectasis, pneumonia, pulmonary edema, hyperglycemia, hypovolemia, hypervolemia, and adhesions.
Peritonitis, the most common problem, is usually caused by failure to use aseptic technique and is characterized by fever, cloudy dialysate, leukocytosis, and abdominal discomfort.
As noted above, in peritoneal dialysis, sterile peritoneal solution is infused into a patient's peritoneal cavity using a catheter that has been inserted through the abdominal wall. The solution remains in the peritoneal cavity for a dwell period. Osmosis exchange with the patient's blood occurs across the peritoneal membrane, removing urea and other toxins and excess water from the blood. Ions that need to be regulated are also exchanged across the membrane. The removal of excess water results in a higher volume of fluid being removed from the patient than is infused. The net excess is called ultrafiltrate, and the process of removal is called ultrafiltration. After the dwell time, the dialysate is removed from the body cavity through the catheter.
Peritoneal dialysis requires the maintenance of strict sterility because of the high risk of peritoneal infection. The risk of infection is particularly high due to the long periods of time that the patient is exposed to the dialysate.
In one form of peritoneal dialysis, which is sometimes referred to as cycler-assisted peritoneal dialysis, an automated cycler is used to infuse and drain dialysate. This form of treatment can be done automatically at night while the patient sleeps. One of the safety mechanisms for such a treatment is the monitoring by the cycler of the quantity of ultrafiltrate. The cycler performs this monitoring function by measuring the amount of fluid infused and the amount removed to compute the net fluid removal.
The treatment sequence usually begins with an initial drain cycle to empty the peritoneal cavity of spent dialysate, except on so-called “dry days” when the patient begins automated treatment without a peritoneum filled with dialysate. The cycler then performs a series of fill, dwell, and drain cycles, typically finishing with a fill cycle.
The fill cycle presents a risk of over-pressurizing the peritoneal cavity, which has a low tolerance for excess pressure.
In traditional peritoneal dialysis, a dialysate container is elevated to certain level above the patient's abdomen so that the fill pressure is determined by the height difference.
Automated systems sometimes employ pumps that cannot generate a pressure beyond a certain level, but this system is not foolproof since a fluid column height can arise due to a patient-cycler level difference and cause an overpressure.
A reverse height difference can also introduce an error in the fluid balance calculation because of incomplete draining.
Modern cyclers may fill by regulating fill volume during each cycle. The volume may be entered into a controller based on a prescription. The prescription, which also determines the composition of the dialysate, may be based upon the patient's size, weight, and other criteria.
Due to errors, prescriptions may be incorrect or imperfectly implemented resulting in a detriment to patient well-being and health.
Systems that measure pressure have been proposed. For example, a pressure sensor in contact with a fluid circuit at the cycler has been described. The sensor indicates the pressure at the proximal end of the fill/drain line. During operation, a controller connected to the pressure sensor changes the operation of the peritoneal dialysis machine in response to changes in pressure sensed by the pressure sensor.
Examples of peritoneal dialysis system are described in U.S. Pat. Nos. 8,267,885; 8,641,659; Published US Patent Application Number 2015/0005699; and Published US Patent Application Number 2016/0008529.
The entire contents of U.S. Pat. Nos. 8,267,885; 8,641,659; Published US Patent Application Number 2015/0005699; and Published US Patent Application Number 2016/0008529 are hereby incorporated by reference.
Peritoneal dialysis is a medical procedure for removing toxins from the blood that takes advantage of the semi-permeable membrane surrounding the walls of the abdomen or peritoneal cavity.
During a peritoneal dialysis procedure, a solution is introduced into the patient's abdomen, where it remains for up to several hours, removing blood toxins via osmotic transfer through the peritoneal membrane. At completion of the procedure, the solution is drained from the body along with the toxins. In automated peritoneal dialysis, the entire procedure is handled by automated equipment; often times in the patient's home while they sleep.
There are many systems for performing automated peritoneal dialysis. Typically, such systems include complex pumping means and a variety of other complex components including noisy pumps and valves to insure accurate delivery of fluid volume and temperature.
In today's economy with the high cost of healthcare, cost is an ever-increasing issue, and many automated peritoneal dialysis equipment manufacturers have attempted to reduce production costs by several means. One is to employ peristaltic pumps, which can be inexpensive, though have inherent limitations.
For example, accurately measuring the fluid volume when delivered by a peristaltic pump can be difficult because the tubing used in the pump is elastic. So consequently, the tubes volume may change over time as well as the pump displacement or rotations must be closely tracked to monitor fluid flow accurately.
Peristaltic pumps also have a tendency to develop pinhole leaks in pump tubing after extended use and can trap fluids between uses which could result in its loss of sterility following repeated uses.
The pump tube is usually a fixed component of the pump and thus is subject to failure due to wear or fracture and can also be difficult to insure its sterility between uses.
Therefore, it is desirable to provide an automated peritoneal dialysis therapy device that delivers temperature controlled volumes of fluids to a patient accurately using a peristaltic pump with both indirect and direct methods of measurement for redundancy.
It is further desirable to provide an automated peritoneal dialysis therapy device that delivers temperature controlled volumes of fluids to a patient accurately using a peristaltic pump by providing a direct determination of fluid volume, flow rate, and temperature using a non-contact solid-state sensor technology.
In addition, it is desirable to provide an automated peritoneal dialysis therapy device that delivers temperature controlled volumes of fluids to a patient accurately using a peristaltic pump by calculating a volume expected to be delivered by tracking effective displacement using a precisely indexed pump motor during actuation and a temperature sensor mounted in close proximity to the tube embedded into the pump base.
Also, it is desirable to provide an automated peritoneal dialysis therapy device that includes a retractable peristaltic pump roller mechanism, which includes cam driven multiple spring loaded pump rollers to allow the patient to easily retract the rollers and insert a disposable peristaltic pump tube into the pump base.
It is desirable to provide an automated peritoneal dialysis therapy device that can facilitate using a peristaltic pump where the pump tube is part of a single use disposable tubing set which can easily be assembled into a retracted pump mechanism by the user during setup, thereby eliminating the need for complex and costly cartridge assemblies and significantly reducing the possibility of system leaks or introduction of non-sterile matter into the patient line.
It is also desirable to provide an automated peritoneal dialysis therapy device that can facilitate using an in-line heating method where the fluid is heated inside the tube section passing through a peristaltic pump, and fluids are heated “on the fly” or simultaneously during the pumping process using heating elements and sensors embedded in the pump housing under a closed loop control process, thereby eliminating the need for heater methods and containers which require large percentages of entire therapy fluid volume (as much as 20 liters) be moved and placed on a bulk heater apparatus by the patient or caregiver and the entire volume heated to the proper temperature before the patients dialysate delivery or therapy can begin.
It is further desirable to provide an automated peritoneal dialysis therapy device that utilizes induction heating of the pump base and rotor and ultimately by conduction and radiation of the tube and the fluid inside.
Moreover, it is desirable to provide an automated peritoneal dialysis therapy device that can facilitate safe and efficacious automated peritoneal dialysis therapy in the privacy of the patient's home or other location where a reliable power source may be available.